The present invention is directed to any field that utilizes parallel arrays of fiber or strand-like components on a scale of a few nanometers to a few millimeters. Such structures may be composed of solid fibers, hollow fibers, or combinations of both solid and hollow fibers. Example structures include, but are not limited to, imaging structures (image fibers, guides, bundles, tapers, and faceplates), multi-hole arrays (photonic crystal structures, capillary arrays), tissue engineering structures (templates, scaffolds), space separated arrays (fiber arrays, post arrays), thermal photovoltaic devices, thermal electric devices, nanoarrays (hole, post), and other devices. Prior art fabrication methods for such structures are quite varied, and some of these methods are described in the following sections.
Imaging Structures
In the field of imaging, and more specifically coherent image guides such as fiber bundles, tapers, and faceplates, it is desirable to create image guides having a very high resolution and maximum brightness at a low cost. Such products, if produced at a low enough cost, can enable a new generation of disposable imaging instruments for medical and industrial use, and hold the promise of increased safety for consumers while also reducing medical costs. For instance, a truly disposable endoscope that is disposed after a single operation will eliminate the transfer of infections from endoscopes due to improper cleaning. While several efforts have demonstrated coherent image guides having either high resolution or somewhat low cost, no image guide product has been introduced to the market that sufficiently satisfies both of these conditions such that truly disposable imaging instruments are available. In addition, medium resolution imaging faceplates, if produced inexpensively, can find mass market consumer application by enabling devices to be manufactured that are too expensive for the market using glass imaging guides.
Imaging guides have long been known in the prior art. Most imaging guides are composed of single core and single clad fibers. Graded index fibers used to form image guides have also long been known in the prior art. Kitano et al, U.S. Pat. No. 3,658,407 (issued 1972), describes the use of graded index fiber to form an imaging guide. In prior art methods for the manufacture of imaging structures, lengths of single core optical fiber (or in some cases, two-dimensional ribbons of single core optical fibers), are fused together under heat and pressure to form a single imaging structure preform, from which imaging structures are fabricated. FIG. 1 shows individual fibers 50 being fused to form an imaging structure perform 52.
Prior art examples also include U.S. Pat. No. 5,881,195, wherein Walker et al. teach a method and instrumentation for fusing optical fibers together to form an image guide. The method described does not indicate how the fibers are bundled prior to fusing. Bundling single fiber lengths is a labor-intensive and costly task that cannot support an extremely low cost production method. Hence U.S. patent application 2002/0168157, also by Walker et al., describes a method for automating some of this work, by extruding 1×N (and up to 3×N) sheets of fibers that are subsequently wound on a spool-like apparatus and fused to form a solid image guide boule. This method, however, limits the packing of fibers to a square arrangement in the cross section, which in turn drastically limits the brightness of the image guide, which is a function of the ratio of core area to cladding area in an image guide.
In U.S. Pat. No. 6,091,872, Katoot describes a method for fusing individual fibers together; however the method is limited in that no simple extension for automating the process is provided. Hence, the method as a whole remains labor-intensive and relatively expensive.
Prior art methods for the manufacture of imaging structures are not cost effective due to the difficulty of transferring (and in some cases aligning) single fibers in a single device to be constructed into a single imaging structures. Additionally, prior art methods require multiple redraw steps in order to manufacture high-resolution imaging structures.
In prior art methods for the manufacture of imaging structures, single core fiber or fiber ribbon is drawn onto a spool or other receiving medium, and then transferred to a device that fuses the fibers together to form an imaging structure preform. The process is repeated as necessary until an imaging structure with desired pixel density is attained. These steps are labor intensive and may introduce imperfections, impurities and/or small particles (e.g. dust or microfibers) to the imaging structures.
Repetitive bundle and redraw steps as described in the prior art introduce line and distortion blemishes, which distort an image that is transferred through imaging structures. Physically ordering individual fiber/pixel elements also introduces line and distortion blemishes. In addition, such steps are labor intensive and take considerable time and cost.
Multi-Hole Arrays
Prior art methods of manufacturing multi-hole arrays are quite varied but the generally involve either the bundling of tubular structures or various other processes.